/*-------------------------------------------------------------------------
 *
 * adminpack.c
 *
 *
 * Copyright (c) 2002-2012, PostgreSQL Global Development Group
 *
 * Author: Andreas Pflug <pgadmin@pse-consulting.de>
 *
 * IDENTIFICATION
 *	  contrib/adminpack/adminpack.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"
#include "knl/knl_variable.h"

#include <sys/file.h>
#include <sys/stat.h>
#include <unistd.h>

#include "catalog/pg_type.h"
#include "funcapi.h"
#include "miscadmin.h"
#include "postmaster/syslogger.h"
#include "storage/smgr/fd.h"
#include "utils/builtins.h"
#include "utils/datetime.h"

#ifdef WIN32

#ifdef rename
#undef rename
#endif

#ifdef unlink
#undef unlink
#endif
#endif

PG_MODULE_MAGIC;

extern "C" Datum pg_file_write(PG_FUNCTION_ARGS);
extern "C" Datum pg_file_rename(PG_FUNCTION_ARGS);
extern "C" Datum pg_file_unlink(PG_FUNCTION_ARGS);
extern "C" Datum pg_logdir_ls(PG_FUNCTION_ARGS);

PG_FUNCTION_INFO_V1(pg_file_write);
PG_FUNCTION_INFO_V1(pg_file_rename);
PG_FUNCTION_INFO_V1(pg_file_unlink);
PG_FUNCTION_INFO_V1(pg_logdir_ls);

typedef struct {
    char* location;
    DIR* dirdesc;
} directory_fctx;

/*-----------------------
 * some helper functions
 */

/*
 * Convert a "text" filename argument to C string, and check it's allowable.
 *
 * Filename may be absolute or relative to the t_thrd.proc_cxt.DataDir, but we only allow
 * absolute paths that match t_thrd.proc_cxt.DataDir or u_sess->attr.attr_common.Log_directory.
 */
static char* convert_and_check_filename(text* arg, bool logAllowed)
{
    char* filename = text_to_cstring(arg);

    canonicalize_path(filename); /* filename can change length here */

    if (is_absolute_path(filename)) {
        /* Disallow '/a/b/data/..' */
        if (path_contains_parent_reference(filename))
            ereport(ERROR,
                (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                    (errmsg("reference to parent directory (\"..\") not allowed"))));

        /*
         * Allow absolute paths if within t_thrd.proc_cxt.DataDir or u_sess->attr.attr_common.Log_directory, even
         * though u_sess->attr.attr_common.Log_directory might be outside t_thrd.proc_cxt.DataDir.
         */
        if (!path_is_prefix_of_path(t_thrd.proc_cxt.DataDir, filename) &&
            (!logAllowed || !is_absolute_path(u_sess->attr.attr_common.Log_directory) ||
                !path_is_prefix_of_path(u_sess->attr.attr_common.Log_directory, filename)))
            ereport(ERROR, (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE), (errmsg("absolute path not allowed"))));
    } else if (!path_is_relative_and_below_cwd(filename))
        ereport(ERROR,
            (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE), (errmsg("path must be in or below the current directory"))));

    return filename;
}

/*
 * check for superuser, bark if not.
 */
static void requireSuperuser(void)
{
    if (!superuser())
        ereport(ERROR,
            (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE), (errmsg("only system admin may access generic file functions"))));
}

/* ------------------------------------
 * generic file handling functions
 */

Datum pg_file_write(PG_FUNCTION_ARGS)
{
    FILE* f = NULL;
    char* filename = NULL;
    text* data = NULL;
    int64 count = 0;

    requireSuperuser();

    filename = convert_and_check_filename(PG_GETARG_TEXT_P(0), false);
    data = PG_GETARG_TEXT_P(1);

    if (!PG_GETARG_BOOL(2)) {
        struct stat fst;

        if (stat(filename, &fst) >= 0)
            ereport(ERROR, (ERRCODE_DUPLICATE_FILE, errmsg("file \"%s\" exists", filename)));

        f = fopen(filename, "wb");
    } else
        f = fopen(filename, "ab");

    if (!f)
        ereport(ERROR, (errcode_for_file_access(), errmsg("could not open file \"%s\" for writing: %m", filename)));

    if (VARSIZE(data) != 0) {
        count = fwrite(VARDATA(data), 1, VARSIZE(data) - VARHDRSZ, f);

        if (count != VARSIZE(data) - VARHDRSZ)
            ereport(ERROR, (errcode_for_file_access(), errmsg("could not write file \"%s\": %m", filename)));
    }
    fclose(f);

    PG_RETURN_INT64(count);
}

Datum pg_file_rename(PG_FUNCTION_ARGS)
{
    char *fn1, *fn2, *fn3;
    int rc;

    requireSuperuser();

    if (PG_ARGISNULL(0) || PG_ARGISNULL(1))
        PG_RETURN_NULL();

    fn1 = convert_and_check_filename(PG_GETARG_TEXT_P(0), false);
    fn2 = convert_and_check_filename(PG_GETARG_TEXT_P(1), false);
    if (PG_ARGISNULL(2))
        fn3 = 0;
    else
        fn3 = convert_and_check_filename(PG_GETARG_TEXT_P(2), false);

    if (access(fn1, W_OK) < 0) {
        ereport(WARNING, (errcode_for_file_access(), errmsg("file \"%s\" is not accessible: %m", fn1)));

        PG_RETURN_BOOL(false);
    }

    if (fn3 && access(fn2, W_OK) < 0) {
        ereport(WARNING, (errcode_for_file_access(), errmsg("file \"%s\" is not accessible: %m", fn2)));

        PG_RETURN_BOOL(false);
    }

    rc = access(fn3 ? fn3 : fn2, 2);
    if (rc >= 0 || errno != ENOENT) {
        ereport(ERROR, (ERRCODE_DUPLICATE_FILE, errmsg("cannot rename to target file \"%s\"", fn3 ? fn3 : fn2)));
    }

    if (fn3) {
        if (rename(fn2, fn3) != 0) {
            ereport(ERROR, (errcode_for_file_access(), errmsg("could not rename \"%s\" to \"%s\": %m", fn2, fn3)));
        }
        if (rename(fn1, fn2) != 0) {
            ereport(WARNING, (errcode_for_file_access(), errmsg("could not rename \"%s\" to \"%s\": %m", fn1, fn2)));

            if (rename(fn3, fn2) != 0) {
                ereport(
                    ERROR, (errcode_for_file_access(), errmsg("could not rename \"%s\" back to \"%s\": %m", fn3, fn2)));
            } else {
                ereport(ERROR, (ERRCODE_UNDEFINED_FILE, errmsg("renaming \"%s\" to \"%s\" was reverted", fn2, fn3)));
            }
        }
    } else if (rename(fn1, fn2) != 0) {
        ereport(ERROR, (errcode_for_file_access(), errmsg("could not rename \"%s\" to \"%s\": %m", fn1, fn2)));
    }

    PG_RETURN_BOOL(true);
}

Datum pg_file_unlink(PG_FUNCTION_ARGS)
{
    char* filename = NULL;

    requireSuperuser();

    filename = convert_and_check_filename(PG_GETARG_TEXT_P(0), false);

    if (access(filename, W_OK) < 0) {
        if (errno == ENOENT)
            PG_RETURN_BOOL(false);
        else
            ereport(ERROR, (errcode_for_file_access(), errmsg("file \"%s\" is not accessible: %m", filename)));
    }

    if (unlink(filename) < 0) {
        ereport(WARNING, (errcode_for_file_access(), errmsg("could not unlink file \"%s\": %m", filename)));

        PG_RETURN_BOOL(false);
    }
    PG_RETURN_BOOL(true);
}

Datum pg_logdir_ls(PG_FUNCTION_ARGS)
{
    FuncCallContext* funcctx = NULL;
    struct dirent* de;
    directory_fctx* fctx = NULL;

    if (!superuser())
        ereport(
            ERROR, (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE), (errmsg("only system admin can list the log directory"))));

    if (strcmp(u_sess->attr.attr_common.Log_filename, "postgresql-%Y-%m-%d_%H%M%S.log") != 0)
        ereport(ERROR,
            (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                (errmsg("the log_filename parameter must equal 'postgresql-%%Y-%%m-%%d_%%H%%M%%S.log'"))));

    if (SRF_IS_FIRSTCALL()) {
        MemoryContext oldcontext;
        TupleDesc tupdesc;

        funcctx = SRF_FIRSTCALL_INIT();
        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);

        fctx = (directory_fctx*)palloc(sizeof(directory_fctx));

        tupdesc = CreateTemplateTupleDesc(2, false);
        TupleDescInitEntry(tupdesc, (AttrNumber)1, "starttime", TIMESTAMPOID, -1, 0);
        TupleDescInitEntry(tupdesc, (AttrNumber)2, "filename", TEXTOID, -1, 0);

        funcctx->attinmeta = TupleDescGetAttInMetadata(tupdesc);

        fctx->location = pstrdup(u_sess->attr.attr_common.Log_directory);
        fctx->dirdesc = AllocateDir(fctx->location);

        if (!fctx->dirdesc)
            ereport(ERROR, (errcode_for_file_access(), errmsg("could not read directory \"%s\": %m", fctx->location)));

        funcctx->user_fctx = fctx;
        (void)MemoryContextSwitchTo(oldcontext);
    }

    funcctx = SRF_PERCALL_SETUP();
    fctx = (directory_fctx*)funcctx->user_fctx;

    while ((de = ReadDir(fctx->dirdesc, fctx->location)) != NULL) {
        char* values[2];
        HeapTuple tuple;
        char timestampbuf[32];
        char* field[MAXDATEFIELDS];
        char lowstr[MAXDATELEN + 1];
        int dtype;
        int nf, ftype[MAXDATEFIELDS];
        fsec_t fsec;
        int tz = 0;
        struct pg_tm date;

        /*
         * Default format: postgresql-YYYY-MM-DD_HHMMSS.log
         */
        if (strlen(de->d_name) != 32 || strncmp(de->d_name, "postgresql-", 11) != 0 || de->d_name[21] != '_' ||
            strcmp(de->d_name + 28, ".log") != 0)
            continue;

        /* extract timestamp portion of filename */
        strcpy(timestampbuf, de->d_name + 11);
        timestampbuf[17] = '\0';

        /* parse and decode expected timestamp to verify it's OK format */
        if (ParseDateTime(timestampbuf, lowstr, MAXDATELEN, field, ftype, MAXDATEFIELDS, &nf))
            continue;

        if (DecodeDateTime(field, ftype, nf, &dtype, &date, &fsec, &tz))
            continue;

        /* Seems the timestamp is OK; prepare and return tuple */

        values[0] = timestampbuf;
        values[1] = (char*)palloc(strlen(fctx->location) + strlen(de->d_name) + 2);
        sprintf(values[1], "%s/%s", fctx->location, de->d_name);

        tuple = BuildTupleFromCStrings(funcctx->attinmeta, values);

        SRF_RETURN_NEXT(funcctx, HeapTupleGetDatum(tuple));
    }

    FreeDir(fctx->dirdesc);
    SRF_RETURN_DONE(funcctx);
}
